There have been numerous attempts over the past few decades to prepare steroids with antihormonal activity. These have been reasonably successful where anti-estrogens and anti-androgens are concerned. However, the discovery of effective antiprogestational and antiglucocorticoid steroids has proved to be a formidable task for the steroid chemist. It has been generally recognized for some years, however, that antiprogestational steroids would find wide applicability in population control, while antiglucocorticoids would be extremely valuable in the treatment of, for example, Cushing's syndrome and other conditions characterized by excessive endogenous production of cortisone. In the last decade, largely through the efforts of Teutsch, et al. of the Roussel-Uclaf group in France, a new series of 19-nortestosterone derivatives has been synthesized with strong affinity for the progesterone and glucocorticoid receptors and with marked antiprogestational and antiglucocorticoid activity in vivo. This important discovery revealed the existence of a pocket in the progesterone/glucocorticoid receptors that is able to accommodate a large 11β-substituent on selected 19-nortestosterone derivatives. By suitable selection of such a substituent, steroids with antihormonal properties were obtained.
The pioneering studies of Teutsch, et al. on the synthesis of antiprogestational and antiglucocorticoid steroids is summarized in a recent review article (G. Teutsch in Adrenal Steroid Antagonism. Ed. M. K. Agarwal, Walter de Gruyter and Co., Berlin, 1984. pp. 43–75) describing the work leading to the discovery of RU-38,486, the first steroid of this type selected for clinical development. RU-38,486 or mifepristone was found to be an effective antiprogestational/contragestative agent when administered during the early stages of pregnancy (IPPF Medical Bulletin 20; No. 5, 1986). In addition to these antiprogestational properties, mifepristone has very significant antiglucocorticoid activity and was successfully used by Nieman, et al. (J. Clin. Endocrinology Metab. 61:536, 1985) in the treatment of Cushing's syndrome. In common with the vast majority of steroidal hormone analogs, mifepristone additionally exhibits a range of biological properties. Thus, for example, it exhibits growth-inhibitory properties towards estrogen-insensitive T47Dco human breast cancer cells (Horwitz, Endocrinology 116:2236, 1985). Experimental evidence suggests that the metabolic products derived from mifepristone contribute to its antiprogestational and antiglucocorticoid properties (Heikinheimo, et al., J. Steroid Biochem. 26:279, 1987).
Ideally, for purposes of contraception, it would be advantageous to have compounds which possess antiprogestational activity without (or with minimal) antiglucocorticoid activity. Although there have been a number of attempts to modify the mifepristone structure in order to obtain separation of the antiprogestational activity from the antiglucocorticoid activity, this goal has not yet been fully achieved. As such, there remains a need in the art for the development of new steroids which possess antiprogestational activity with minimal antiglucocorticoid activity.